Multi-cylinder pulse charging system

ABSTRACT

Disclosed herein is a marine propulsion device comprising an engine having at least three cylinders each with an exhaust port, means for establishing a sequential firing order for said cylinders, and exhaust gas discharge means communicating with said exhaust ports for establishing substantially equal acoustical flow distances between each of said exhaust gas ports and said exhaust port of the subsequently charged one of said cylinders. The acoustical flow distance is uniform so as to afford with respect to each firing of the engine, arrival of a compressive wave emanating from the opening of the exhaust port of one of the said cylinders at the exhaust port of the cylinder which is next charged at a time prior to closing of the last mentioned exhaust port.

United States Patent Miller et al.

MULTI-CYLINDER PULSE CHARGING SYSTEM 1 51 Sept. 19, 1972 FOREIGN PATENTS OR APPLICATIONS 886,556 /1943 France ..60/32 M Inventors: George e Zion; Paul 678,119 3/ 1930 France ..60/32 M Kalb, waukegan, both of 966,932 9/ 1957 Germany ..60/32 M 73 A z 0 tboard M i C ration Germany M 1 sslgnee w'gukegan, m m 363,382 12/1931 Great Britain ..60/32 M 3,850 0/1903 Great Britain ..123/ V [22] Filed: July 13, 1970 21 App] 54 1 Primary Examiner-Wendell E. Burns Attorney-Robert K. Gerling, Robert E. Clemency, John W. Michael, Gerrith D. Foster, Ba ard H. [52] US. Cl. ..123/55 VE, /273, 60/312, Michael Paul Puemer, Joseph A Germignini, Am

60/314 23/65 123,52 123/55 drew O. Riteris and Spencer B. Michael US [51] Int. Cl ..F0lr 7/08, B63h 21/26, F01r H00 [58] Field of Search.....60/29, 32, R, 32 M, 314, 312, [57] ABSTRACT 60/223; 123/65 E, 55 V, 55 VS, 55 VE; Disclosed herein is a marine propulsion device com- 115/17 prising an engine having at least three cylinders each with an exhaust port, means for establishing a sequen [56] References Cited tiai tiring order for said cylinders, and exhaust gas discharge means communicating with said exhaust UNITED STATES PATENTS ports for establishing substantially equal acoustical 2,476,816 7/1949 Carter ..123/ 1 flow distances between each of said exhaust gas ports 2,858,667 11/1958 Reske ..60/29 X and said exhaust port of the subsequently charged one 3,507,301 1970 Larson -.60/32 M of said cylinders. The acoustical flow distance is 3,045,423 7/1962 Hulsebus ..60/32 uniform so as to afford with respect to each firing of 3,470,690 l0/1969 Thompson M the engine, arrival of a compressive wave emanating 3,385,052 5/1968 Qlterman a1 X from the opening of the exhaust port of one of the said 3,520,270 7/1970 M111er ..115/17 cylinders at the exhaust port f the cylinder which is 2,921,567 l/l960 Medenus ..123/55 V next charged at a time prior to closing of the last 3,233,598 2/1966 Van Ranst 123/55 V honed exhaust port. 2,166,968 7/1939 Rohlin ..123/55 VE 3,470,690 10/ 1969 Thompson ..60/32 M 18 Claims, 13 Drawing Figures PATENTEDSEP 19 m2 SHEET 1 BF 4 939 @MQZQM/ Mm. (M

PAIENTEHSEPIQIW? 3.692 006 SHEET 3 [IF 4 MULTI-CYLINDER PULSE CHARGING SYSTEM BACKGROUND OF THE INVENTION The invention relates generally to two stroke engines for marine propulsion devices and particularly to exhaust systems for such two stroke engines. Still more particularly, the invention relates to multi-cylinder two stroke internal combustion engines and to arrangements for discharging exhaust gases so as to increase engine horsepower.

In general, it is known to utilize returning pressure waves to improve scavenging, thereby to increase the amount of fuel mixture in the next charge and thereby to boost horsepower. It has also been known to apply a compressive pulse from an exhaust gas system to a cylinder just prior to closing of the exhaust port so as to raise the pressure of the fuel mixture in the cylinder and thus effect a supercharge and/or to effectively stop the flow of fresh charge from the exhaust port and thus reduce loss of fuel.

In this regard, U.S. Pat. No. 3,385,052, issued May 28, 1968 to T. J. l-loltermann et al. discloses a single cylinder, two stroke internal combustion engine wherein the compressive pressure waves or pulses set up in the exhaust system of the engine by the discharge of exhaust gases are returned to the exhaust port of the cylinder as compressive pressure waves to thereby utilize such pressure waves to increase the efficiency and ultimately the horsepower of the engine.

U.S. Pat. No. 3,385,052 also discloses controlling the time of arrival of a returning pressure wave, i.e., either a positive or compressive wave, or a negative or rarefactive wave at the originating cylinder.

U.S. application Ser. No. 733,159 now U.S. Pat. No. 3,520,270 filed May 29, 1968 by George Miller discloses an outboard motor with a multicylinder two stroke engine.'The outboard motor includes several arrangements within the drive shaft housing for employing a negative or rarefactive pressure wave to assist in scavenging the cylinder originating the pressure wave from which the rarefactive wave is generated.

U.S. application Ser. No. 746,079, now U.S. Pat. No. 3,543,509 filed on July 19, 1968, by Michael J. Boerma discloses an outboard motor having three vertically inline cylinders and an exhaust gas system including a baffle for equalizing back-pressure on the three cylinders to provide smooth idling operation.

U.S. application Ser. No. 26,843 was filed on Apr. 9, 1970, by Michael J. Boerma and discloses an outboard motor including a two cylinder, two stroke engine. Included in the outboard motor is an exhaust gas arrangement which is designed so that a compressive wave originating at one cylinder is reflected by the closed exhaust port of the other cylinder for return to the originating cylinder so as to arrive at the originating cylinder prior to exhaust port closing and thereby increase horsepower output.

Acoustical flow, as this term is employed in this application takes place at or near the speed of sound and is primarily affected by the static stream temperature of the exhaust gas, i.e., the static temperature of the surrounding environment. Acoustical flow is essentially independent of the cross sectional area or configuration of the path through which the flow occurs, except for generation of return pulses, either rarefactive or compressive, in response to changes in cross sectional flow area, and except for the speed of travel, if any, of the mass flow or medium through which the acoustical flow propagates. The mass flow of the exhaust product is dependent, at least in part, on the configuration of the exhaust gas path and upon the pressure differential associated with the path. In exhaust gas flow systems for two stroke engines, the mass flow of the exhaust product is comparatively slow as compared to the rate of acoustical flow and, thus, the acoustical flow is usually not substantially affected by changes in configuration of the exhaust gas path or by pressure differential associated with the path. Accordingly,

acoustical flow in paths of equal length will generally have the same characteristics, as for instance, the time for flow through one path will be substantially the same as the time for flow through any path of equal length.

SUMMARY OF THE INVENTION The invention provides apparatus for increasing the effective horsepower of an internal combustion engine which has three or more cylinders.

In accordance with the invention, there is provided an outboard motor having a two stroke internal combustion engine with at least three cylinders and with an exhaust gas system such that the acoustical flow distance from each of the exhaust ports to the exhaust port of the cylinder next to be charged is substantially the same. The acoustical flow distance is chosen so as to afford arrival of the compressive wave occurring incident to exhaust port opening at the exhaust port of the cylinder just fired at a time prior to exhaust port closing of the next cylinder to be charged. As a consequence, the portion of the combustable charge which, in the past, has been lost through the exhaust system, is decreased and pressure in the cylinder at the time of exhaust port closing is believed to be increased.

More particularly, in accordance with the invention, there is provided an outboard motor comprising a twostroke internal combustion engine having an engine block with more than two cylinders, said cylinders each having an exhaust port and, a lower unit including a drive shaft housing supporting said engine block at the top of said housing, a part connected to said drive shaft housing and extending, under normal operating conditions, into the water, a propeller supported by said part, an exhaust gas pipe extending at least partially within said housing and having one end located adjacent to the top of said housing, and an exhaust gas passageway system located above the upper end of the exhaust gas pipe and including an outlet passageway communicating with the upper end of the exhaust gas pipe and respective passageways communicating with each of the exhaust gas ports and with the outlet passageway so as to provide substantially equal acoustical flow distances between each of the exhaust gas ports and the exhaust gas port of the cylinder being charged at the time of the opening of the exhaust gas port of the immediately previously fired cylinder.

In one embodiment disclosed herein, there is disclosed a V4 engine having an exhaust gas system including an exhaust pipe structure which communicates with all of the exhaust ports and has a common outlet or discharge in the interior of the drive shaft housing. In accordance with the invention, the acoustical flow path from the outlet or discharge to all of the ports is substantially the same. Thus, the exhaust gas system is arranged to provide, incident to exhaust port opening Subsequent to firing, a rarefaction wave which is applied through the exhaust port of the just fired cylinder so as to increase scavenging. Also in this embodiment, the exhaust gas system includes four branch passages which are joined together so that the acoustical fiow distance from each of the exhaust ports to the exhaust port of the next to be charged cylinder is substantially equal.

Equalization of the acoustical flow distances between the exhaust ports of the cylinders previously fired and the exhaust ports of the cylinders next to be charged is provided by a passageway structure which is connected between the engine block and a member sandwiched between the engine block and the drive shaft housing. The passage structure is provided with a common outlet for discharge of exhaust gases into a duct in the member and with various branch passageways to provide the substantially equal acoustical flow paths. The exhaust duct in the sandwiched member extends downwardly and forwardly and empties into an exhaust pipe structure which extends into the drive shaft housing and has a portion of increased cross section as compared to the cross section at the junction with the exhaust duct in the sandwiched member. In addition, the exhaust passage structure is provided with a water jacket around the passageways.

The invention also provides a method of operating a multi-cylinder two-stroke internal combustion engine having more than two cylinders comprising sequen tially firing all of the cylinders in a predetermined series, and sequentially causing, with respect to all of the cylinders, arrival of the compressive wave emanating from the opening of the exhaust port of the immediately previously fired cylinder at the exhaust port of the cylinder then being charged at a uniform time with respect to exhaust port closure for a given engine speed condition, and also sequentially causing, with respect to all of the cylinders, generation by the compressive waveemanating from the exhaust port of the previously fired cylinder of a rarefaction wave which arrives at the exhaust port of the previously fired cylinder at a uniform time prior to closure of said exhaust port of the previously fired cylinder for a given engine speed.

One of the principal objects of the invention is the provision of a method for applying compressive waves occurring incident to opening of the exhaust ports of the cylinders just fired to the open ports of the exhaust ports of the cylinders next to be charged so as to increase effective horsepower output. Another principal object of the invention is the provision of an outboard motor with a new and novel exhaust system which provides increased horsepower as compared to previous outboard motors of similar construction but without the novel exhaust system.

Still another object of the invention is the provision of an exhaust gas system which can be applied to an existing outboard motor or which can be integrally designed in an outboard motor to provide superior outboard motor performance.

Still another object of the invention is the provision of a marine propulsion device having an engine which has at least three cylinders and in which acoustical flow distances between the exhaust ports of all of the cylinders and the exhaust ports of the cylinders next to be charged are substantially the same.

Another object of the invention is the provision of an engine asdescribed in the preceding paragraph and in which the acoustical flow distances between the exhaust ports of all of the cylinders and a common discharge or outlet is the same.

Still another object of the invention is the provision of an improved marine propulsion device such as, for instance, an outboard motor having an improved exhaust system which contributes to increased horsepower while, at the same time, provides for relatively quiet operation due to employment of underwater exhaust.

Other objects and advantages of the invention wil become known by reference to the following description and accompanying drawings.

DRAWINGS FIG. 1 is a fragmentary elevational view, shown partially schematically and partially in section, of an outboard motor embodying various of the features of the invention.

FIG. 2 is a rear end elevational view, partially broken away and in section, of a portion of the exhaust gas passage structure embodied in the outboard motor shown in FIG. 1.

FIG. 3 is a perspective front end view of the exhaust gas passage structure shown in FIG. 2.

FIGS. 4 and 5 are perspective views of filler blocks which can be employed in adapting an existing engine to incorporate the features of the disclosed invention.

FIG. 6 is a horizontal sectional view taken generally along line 6-6 of FIG. 1.

FIG. 7 is an inside-out schematic view of the exhaust passage system provided in the outboard motors shown in FIG. 1.

FIG. 8 is an inside-out schematic view of an exhaust gas passage system which embodies various of the features of the invention and which is adapted for a 3- cylinder in-line engine.

FIG. 9 is an inside-out" schematic view of an exhaust gas passage system which embodies various of the features of the invention and which is adapted for a 4- cylinder in-line engine.

FIG. 10 is an inside-out schematic view of an exhaust gas passage system which embodies various of the features of the invention and which is adapted for a 6- cylinder V-configuration.

FIG. 11 is an inside-out schematic view of an exhaust gas passage system which embodies various of the features of the invention and which is adapted for a 6- cylinder in-line configuration.

FIG. 12 is a sectional view on a reduced scale taken generally along line 12-12 of FIG. 6.

FIG. 13 is a schematic view of the exhaust gas system arrangement.

GENERAL DESCRIPTION Shown in FIG. 1 is an outboard motor 11 embodying various of the features of the invention. The outboard motor 11 includes a power head 13 and a lower unit structure 17 which supports the power head 13.

The power head 13 comprises an engine 19 having a V-block 21 (See FIG. 6) with first and second cylinder banks 23 and 27 located at an angle of 90 with respect to each other. The first bank 23 of cylinders includes (See FIG. 12) first and second cylinders 29 and 31 with the second cylinder 31 being located below, and parallel to, and in alignment with, the first cylinder 29 having its axis in a first plane which also contains the axis of the first cylinder. The second bank 27 of cylinders includes third and fourth cylinders 33 and 37 with the fourth cylinder 37 being located below, and parallel to, and in alignment with, the third cylinder 33 and with the axis of the fourth cylinder 37 being located in a second plane which also contains the axis of the third cylinder 33 and which is located at an angle of 90 with respect to the first mentioned plane.

The cylinders 29, 31, 33, and 37 respectively include pistons (not shown) which are respectively joined by connecting rods (not shown) to a common vertically extending crankshaft or drive shaft 46. The cylinders 29, 31, 33, and 37 further respectively include exhaust ports 39, 41, 43, and 47 which open rearwardly in the area between the cylinder banks 23 and 27. More specifically, the exhaust ports 39 and 41 of the bank 23 enter into a chamber 48 which is separated from a like chamber 49 communicating with the exhaust ports 43 and 47 of the other cylinder bank 27 by a vertically extending partition 50 which, together with the other portions of the engine block, forms a face 51 which extends perpendicularly to a line bisecting the included angle between the cylinder banks 23 and 27. In prior constructions, the chambers 48 and 49 communicated with each other at their bottom and discharged into a common exhaust conduit. As a consequence, the acoustical flow distances between subsequently fired cylinders varied.

The engine is also provided with means 53 for establishing a sequential firing order. Such means are well known in the art and will not be specifically described except to state that in the disclosed construction, the cylinders 29, 31, 33, and 37 fire in the following order: 33: 29:37: 31.

The lower unit structure 17 supports the power head 13 and includes at the upper end thereof, an adapter or member 54 which is bolted or otherwise solidly connected to the engine block 21, and an exhaust gas or drive shaft housing 57 which, at its upper end, is solidly connected to the adapter 53 and which, at its lower end, supports a gear box (not shown) containing a propeller shaft (not shown) and a reversing transmission (not shown). As thus far disclosed, the construction is entirely conventional.

In accordance with the invention, an exhaust gas passage means or discharge system is provided for conducting exhaust gases so that compressive waves emanating from opening of any of the exhaust ports 39, 41, 43, and 47 will arrive at the open exhaust port of the cylinder next to be charged just prior to the time of exhaust port closure. The system is also designed so that the outgoing compressive wave will generate a returning rarefaction wave which arrives back at the originating cylinder at about the time when the piston is at bottom dead center to increase scavenging.

More specifically, the exhaust gas passage or discharge means 71 includes means'for conducting exhaust gases from the exhaust ports 39, 41, 43, and 47 so as to provide substantially uniform acoustical flow paths between each of the exhaust ports and the exhaust port of the cylinder which is next charged. In addition, the exhaust gas passage means is arranged so that the acoustical flow distance between the exhaust gas port of the cylinder which has just fired and the exhaust gas port of the cylinder which will be charged next is such that a compressive wave emerging from the previously fired cylinder will arrive, under normal operating temperatures, and when the engine is operating in the high speed range, at the exhaust port of the next cylinder to be charged, shortly in advance of the closing of the exhaust port of the next cylinder to be charged. As a consequence, all of the cylinders will be subject to a pressure increase just prior to closing of the associated exhaust port by a compressive wave originating from the previously fired cylinder.

In the particularly disclosed construction, the exhaust gas passage means comprises exhaust gas passage duct or structure 73 (See FIG. 2) communicating with the exhaust ports 39, 41, 43, and 47 and with an exhaust conduit or duct 77 in the adaptor 54 (See FIG. 1). In turn, the exhaust duct 77 communicates with an exhaust gas pipe structure 79 which, in the disclosed construction, is supported from the adaptor 54 and extends downwardly and forwardly into the interior of the drive shaft or gas housing 57.

In accordance with the invention and as shown diagrammatically in FIGS. 7 and 13, the exhaust gas passage structure 73 includes wall means defining a branch passageway portion 81 which communicates with the exhaust port 39 and a branch passageway portion 83 which communicates with the exhaust port 41. At an equal acoustical flow distance from the exhaust ports 39 and 41, the branch passageway portions 81 and 83 are joined to provide a branch passageway 87.

In a similar fashion, the exhaust gas passage structure 73 also includes wall means defining a branch passageway portion 89 which communicates with the exhaust port 43 and a branch passageway portion 91 which communicates with the exhaust port 47. At an equal acoustical flow distance from the exhaust ports 43 and 47, the branch passageway portions 89 and 91 join to provide a passageway branch 93. At an equal acoustical flow distance from the junctures of the branch passageway portions, the branch passageways 87 and 93 join each other to provide a passageway 97 which includes an outlet 99 communicating with the exhaust duct 77.

The wall means providing the above passageway system is, preferably, formed without abrupt changes to afford smooth mass flow and to reduce, as far as possible, pressure waves generated by cross sectional variations and can be formed from one or more elements or members to provide the desired system.

In order to modify the previous exhaust gas system to obtain the features of the invention, the engine 19 shown in FIG. 6 is modified to include, in each of the chambers 48 and 49, respective filler blocks I11 and 113 which substantially occupy the entire area of the chambers 48 and 49 and which have lips extending to and mating with the area of the engine block around the exhaust ports. The filler blocks 111 and 113 are also provided with passages which can be considered either as extensions of the exhaust ports, which extensions extend to the face 51 for communication with the branch passageway portions previously described or as parts of the branch passageway portions, which parts extend to the exhaust ports 39, 41, 43, and 47. More particularly, the filler block 111 (See FIG. includes exhaust passages 117 and 119 which respectively communicate with the exhaust ports 39 and 41 and with the branch passageway portions 81 and 83 and the filler block 113 (See FIG. 4) includes exhaust passages 121 and 123 which communicate with the exhaust ports 43 and 47 and with the branch passageway portions 89 and 91. As a consequence, exhaust flow from the ports is delivered through the passages 117, 119, 121, and 123 and past the face 51 of the engine block 21 into the passageway structure 73.

In the disclosed construction, the passageway structure 73 is provided by a member 127 which includes the before mentioned wall means defining the passageway 97, the branch passageways 87 and 93 and the branch passageway portions 81, 83, 89, and 91. In addition, the member 127 includes wall means partially defining a water jacket 129 (See FIGS. 1 and 2) which is completed by a removable cover 131. Appropriate means for supplying water and draining water from the jacket 129 can also'be included.

The member 127 is suitably detachably connected, as by bolts 133, or otherwise, to the face 51 of the engine block 21 and to a part 137 of the adaptor member 54 which includes the exhaust duct 77 so as to communicate the outlet 99 with the exhaust duct 77.

The exhaust gas flow is from the outlet 99 through the exhaust duct 77 to the pipe structure 79 having a discharge 80 into the interior of the drive shaft housing 57. In this regard, the ratio of the cross sectional area at the discharge 80 of the pipe structure 79 to the cross discharge. Such atmospheric discharge, however, is undesirable as compared to underwater discharge because of the attendant high noise level. Direct discharge to the atmosphere is also relatively undesirable as compared to underwater discharge rearwardly of the propeller hub in a through-the-prop or other like arrangement because the exhaust discharge into the void behing the propeller tends to create a partial vacuum and to result in a lower back-pressure on the engine, thereby increasing horsepower output.

Shown in FIG. 8 is a schematic inside-out view of an exhaust gas passage system or means 271 which communicates with the aligned exhaust ports of a 3- cylinder in-line engine and which includes three branch passageways 287, 293, and 295 which afford equal acoustical flow paths from all of the exhaust ports to a common junction 296 with a discharge passageway 297 having an outlet 299. In addition, the flow path to the junction 296 is designed so that, whatever the firing sectional area within the drive shaft housing 57 is greater than 1:5. Accordingly, exhaust gas compressive waves traveling from the pipe structure 79 into the interior of the drive shaft housing 57 will generate rarefaction waves which will return up the exhaust gas pipe structure, through the duct and passage structure to the exhaust ports. The length of the pipe structure 79 is so designed so that the over-all length from the discharge 80 to the exhaust ports 39, 41, 43, and 47 will cause arrival of rarefaction waves at the exhaust ports of the originating cylinders approximately when the pistons are near bottom dead center when the engine is operating at normal temperature conditions in the high speed range.

In the disclosed construction, from the interior of the drive shaft housing 57, the exhaust gas can flow either to a through-the-prop discharge or to a discharge through a fin, both of which underwater discharges are of conventional construction and need not be specifically described. However, it is important to note that the invention affords the advantages of underwater discharge while, at the same time, increased horsepower output is obtained. The arrangement can also employ the features of the Miller application Ser. No. 733,159 filed May 29, 1968 to obtain rarefaction waves while simultaneously obtaining the sound reducing features of the exhaust gas tube water jacket disclosed in the Miller application.

It should also be noted, that the exhaust gas discharge means can, if desired, be directly open to the atmosphere rather than employing underwater order, there will always be a common acoustical flow distance between the exhaust port of the first fired cylinder and the exhaust port of the cylinder next to be charged such that, at high engine speeds, a compressive wave emanating from the opening of the exhaust port of the cylinder just fired will arrive at the exhaust port of the cylinder next to be charged just prior to closure of the port. Still further, the discharge passage 297 has a length such that, ahigh engine speeds, the exhaust gas flow from the outlet 299 will generate a rarefaction wave which will return to the originating cylinder, desirably about the time when the associated piston is adjacent to bottom dead center, to thereby improve scavenging.

It should be further noted that the discharge passageway can be open directly to the atmosphere or can terminate within a drive shaft housing to take advantage of commonly known underwater exhaust systems and the quieter operation afforded thereby. In addition, it should also be noted that the exhaust system in the drive shaft housing can employ the features disclosed in the Miller application Ser. No. 733,159 filed May 29, 1968 to obtain rarefaction waves to increase scavenging while simultaneously affording still quieter operation by employing the exhaust gas tube water jacket feature of the Miller application Ser. No. 733,159.

Shown in FIG. 9 is a schematic inside-out view of an exhaust passage system or means 371 which communicates with the aligned exhaust ports of a 4- cylinder in-line engine and which includes branch passageways 387, 393, 394, and 395 which afford equal acoustical flow paths from all of the exhaust ports to a more or less common junction 396 with a discharge passageway 397 having a discharge outlet 399. As with respect to the system 271 shown in FIG. 8, the flow path to the junction 396 is designed so that, whatever the firing order, there will always be a common acoustical flow distance between the exhaust port of the first fired cylinder and the exhaust port of the cylinder next to be charged such that, at high engine speeds, a compressive wave emanating from the opening of the exhaust port of the cylinder just fired will arrive at the exhaust port of the cylinder next to be charged just prior to closure of the port. Still further, the discharge passage 397 has a length such that, at high engine speeds, the exhaust gas flow from the outlet will generate rarefaction waves which will return to the originating cylinder, desirably about the time when the associated piston is adjacent to bottom dead center, to thereby improve scavenging.

It should be further noted that the discharge passageway can be open directly to the atmosphere or can tenninate within a drive shaft housing to take advantage of commonly known underwater exhaust systems and the quieter operation afforded thereby. In addition, it should also be noted that the .exhaust system in the drive shaft housing can employ the features disclosed of the Miller application Ser. No. 733,159 filed May 29, 1968 to obtain rarefaction waves to increase scavenging while simultaneously affording still quieter operation by employing the exhaust gas tube water jacket feature of the Miller application Ser. No. 733,159.

Shown in FIG. 10 is a schematic inside-out view of a dual exhaust gas arrangement 470 which communicates with the exhaust ports of a V-block enging having two banks each having three cylinders. The cylinders in each bank are arranged to fire at 120 intervals of crankshaft rotation and the dual exhaust arrangement 470 is arranged as if the engine were, in effect, two integrated 3-cylinder engines. Thus, the exhaust gas passage arrangement 470 shown in FIG. 10 includes two exhaust gas passage systems 471 and 472 which are generally identical and which are essentially the same as the exhaust gas passage system 271 disclosed in FIG. 8. Accordingly, no further description is provided herein.

Shown in FIG. 11 is an exhaust gas discharge arrangement for a 6-cylinder in-line engine. As shown, the in-line six exhaust ports are provided with a dual exhaust gas passage arrangement 570 which, in effect, is the equivalent of the arrangement 470 provided for the 6-cylinder V-configuration shown in FIG. 10. More specifically, the cylinders which are fired at 120 intervals of crankshaft rotation are integrated into one exhaust gas passage system 571, while the remaining exhaust ports are integrated into a second exhaust gas passage system 572. Each of the systems 571 and 572 is essentially identical to the 3-cylinder in-line system 271 shown and described with respect to FIG. 8 and, accordingly, will not be further described.

It is noted that the interval between exhaust port opening and closing decreases with increasing speed of engine rotation and that the time interval between successive operations of the exhaust ports of a multicylinder engine decreases with an increase in the number of cylinders, notwithstanding that the acoustical flow velocity is essentially independent of the operating speed and of the number of cylinders. Thus, for a given speed of operation, there is a lesser time intervals between successive operations in a 2-cylinder engine as compared to a single cylinder engine and there is a still lesser time intervals between successive cylinder operations in a 3-cylinder engine as compared to a 2-cylinder engine.

The pulse charging feature of this invention is therefor dependent, at least in part, on the presence of more than two cylinders, because, in general, the time interval between successive port operations in a 2- cylinder engine is not conducive to pulse charging the cylinder next to be charged by the previously fired cylinder. In addition, optimum results are achieved at a given engine speed as the time interval between successive exhaust port operations is determined, at least in part, by engine speed. It should also be noted that because the successive operations of a 6-cylinder engine occur at too short an interval to effectively accomplish the pulse charging and scavenging features of the invention, the 6-cylinder engine is treated, in effect, as two 3-cylinder engines.

It is also to be noted that in the'construction disclosed in FIGS. 1 through 13, the acoustical flow distances between each of the exhaust ports and the exhaust port of the next to be fired cylinder, or the cylinder being charged at the time of the opening of the exhaust gas port of the previously fired cylinder, is the same. Particularly with respect to the embodiments of FIGS. 1 through 7, l2, and 13, both the cylinder next to be fired and the cylinder being charged at the time of the opening of the exhaust gas port of the previously fired cylinder, are located in the other bank from the immediately previously fired cylinder.

It is also to be noted that pulse charging from the cylinder just fired to the next cylinder to be charged is more effective than employing a reflected compressive wave for self-charging of the cylinder from which the compressive wave originated. The greater effectiveness is provided because of the shorter path length from the origination of the compressive wave to the application of the compressive wave and because of the consequent lesser energy loss which affords consequent 1 greater supercharging capacity.

Various of the features of the invention are set forth in the following claims.

What is claimed is:

1. An outboard motor comprising a two-stroke internal combustion engine having a first cylinder bank in cluding a first cylinder and a second cylinder arranged parallel to and in alignment with said first cylinder and having an axis in a first plane containing the axis of said first cylinder, a second cylinder bank including a third cylinder and a fourth cylinder arranged parallel to and in alignment with said third cylinder and having an axis in a second plane containing the axis of said third cylinder, said second plane being at an angle with respect to said first plane, said cylinders each having an exhaust port, means for firing said first, second, third, and fourth cylinders in a predetermined sequential order, a lower unit including a drive shaft housing supporting said engine at the top of said housing, a part which extends, under normal operating conditions, into the water, a propeller supported by said part, and an exhaust gas pipe extending at least partially within said housing and having an upwardly open end adjacent to the top of said housing, and an exhaust gas passageway system located above said one end of said exhaust gas pipe and communicating with said exhaust gas ports and having a downwardly open outlet communicating with said upwardly open end of said exhaust gas pipe, said exhaust gas passageway system providing substantially equal acoustical flow distances between each of said exhaust gas ports and said exhaust gas port of the cylinder being charged at the time of the opening of the exhaust gasport of the immediately previously fired cylinder, said acoustical flow distances having a length such that the compressive wave emanating from opening of the exhaust gas port of the immediately previously fired cylinder arrives at the exhaust gas port of the then being charged cylinder at a time prior to closure of said exhaust gas port of the cylinder then being charged.

2. An outboard motor in accordance with claim 1 wherein the angle between said first plane and said second plane is approximately 90.

3. An outboard motor in accordance with claim 1 wherein said exhaust gas ports are open in the area between included angle between said first and second planes.

4. An outboard motor in accordance with claim 1 wherein said exhaust gas pipe structure includes an area of increased cross section as compared to the cross section of said pipe structure adjacent to said exhaust gas passage system.

5. An outboard motor comprising an engine having a block including a first cylinder bank having a first cylinder and a second cylinder arranged parallel to and in alignment with said first cylinder and having an axis in a first plane containing the axis of said first cylinder, a second cylinder bank including a third cylinder and a fourth cylinder arranged parallel to and in alignment with said third cylinder and having an axis in a second plane containing the axis of said third cylinder, said second plane being at an angle with respect to said first plane, said engine block also including a face extending generally perpendicularly to a line bisecting the angle between said first and second planes, and cylinders each having an exhaust port, means for firing said first, second, third, and fourth cylinders in a predetermined sequential order, a housing structure supporting said engine and including an outer housing and an exhaust gaspipe extending at least partially within said housing, and an exhaust gas passageway system communicating between each of said exhaust ports and said exhaust gas pipe, said exhaust gas passageway system providing substantially equal acoustical flow distances between each of said exhaust ports and said exhaust gas port of the subsequently fired one of said cylinders, said exhaust gas passageway system including exhaust gas passages in said engine block communicating with said exhaust ports and with said face, said passageway system further including a passage structure connected to said face of said block, having a single exhaust gas outlet communicating with said exhaust gas pipe and located in a surface in a plane at a substantial angle to said face of said block, and internal passageways communicating between said outletand each of said gas passages such that the acoustical flow path from said outlet to each of said exhaust ports is approximately e ual.

6. An outboard motor in accordance with claim 5 wherein said passage structure is provided with a jacket adapted to contain a flow of cooling water.

7. An outboard motor in accordance with claim 5 wherein said engine includes a member between and connected to said engine block and said housing structure and said member includes a part connected to said surface of said passage structure and an exhaust gas duct communicating through said part with said outlet of said passage structure and communicating with said exhaust gas pipe of said housing.

8. An outboard motor in accordance with claim 7 wherein said face of said engine block is at the rear of the outboard motor and said exhaust duct in said member extends downwardly and forwardly.

9. An outboard motor comprising a two-stroke internal combustion engine having an engine block with more than two cylinders, said cylinders each having an exhaust port, a lower unit including a drive shaft housing supporting said engine block at the top of said housing, a part connected to said drive shaft housing and extending, under normal operating conditions, into the water, a propeller supported by said part, and an exhaust gas pipe extending at least partially within said housing and having one end located adjacent to the top of said housing, and an exhaust gas passageway system located above said one end of said exhaust gas pipe and including an outlet passageway communicating with said one end of said exhaust gas pipe and respective passageways communicating with each of said exhaust ports and with said outlet passageway so as to provide substantially equal acoustical flow distances between each of said exhaust gas ports and said exhaust gas port of the cylinder being charged at the time of the opening of the exhaust gas port of the immediately previously fired cylinder, said acoustical flow distances having a length such that the compressive wave emanating from opening of the exhaust gas port of the immediately previously fi'red cylinder arrives at the exhaust gas port of the cylinder then being charged at a time prior to closure of said exhaust gas port of the cylinder then being charged.

10. An outboard motor in accordance with claim 9 wherein said engine block includes three cylinders communicating with said exhaust gas passageway system.

11. An outboard motor in accordance with claim 9 including four cylinders communicating with aid exhaust gas passageway system.

12. An outboard motor in accordance with claim 9 wherein said one end of said exhaust gas pipe is upwardly open and said outlet passageway is downwardly open.

13. An outboard motor in accordance with claim 9 wherein said lower unit includes an adaptor member located between said engine block and said drive shaft housing and including an exhaust gas duct communicating between said outlet passageway and said exhaust gas pipe.

14. An outboard motor in accordance with claim 9 including a water jacket in cooling relation to said exhaust gas passageway system.

15. An outboard motor in accordance with claim 9 wherein said lower unit includes an underwater exhaust gas discharge outlet communicating with said exhaust gas pipe.

16. An outboard motor in accordance with claim 9 wherein said drive shaft housing includes an enlarged conduit portion and wherein said exhaust gas pipe discharges into said enlarged conduit portion and wherein the acoustical flow distances from each of said exhaust port to said enlarged conduit portion is substantially equal.

17. An outboard motor comprising a two-stroke internal combustion engine having an engine block with more than two cylinders, said cylinders each having an exhaust port, and a lower unit including a drive shaft housing supporting said engine block at the top of said housing, a part connected to said drive shaft housing and extending, under normal operating conditions, into the water, a propeller supported by said part, an exhaust gas pipe extending at least partially within said housing and having an upper end located adjacent to the top of said housing and a lower discharge outlet, and an exhaust gas passageway system located above said one end of said exhaust gas pipe and including an outlet passageway communicating with said one end of said exhaust gas pipe and respective passageways communicating with each of said exhaust ports and with said outlet passageway so as to provide substantially equal acoustical flow distances between each of said exhaust gas ports and said exhaust gas port of the cylinder being charged at the time of the opening of the exhaust gas port of the immediately previously fired cylinder, and so as to provide substantially equal acoustical flow distances between each of said exhaust gas ports and said exhaust gas pipe discharge outlet, said acoustical flow distances between said exhaust gas ports having a length such that the compressive wave emanating from opening of the exhaust gas port of the immediately previously fired cylinder arrives at the exhaust gas port of the cylinder then being charged at a time prior to closure of said exhaust gas port of the cylinder then being charged.

18. A method of operating a multi-cylinder twostroke internal combustion engine having more than two cylinders comprising sequentially firing all of the cylinders in a predetermined series, and sequentially causing, with respect to all of the cylinders and for a given engine speed condition, arrival of the compressive wave emanating from the opening of the exhaust port of the previously fired cylinder at the exhaust port of the cylinder then being charged at a uniform time prior to closure of the exhaust port of the cylinder then being charged, and also sequentially causing, with respect to all of the cylinders and for a given engine speed condition, generation by the compressive wave emanating from the exhaust port of the previously fired cylinder of a rarefaction wave which arrives at the exhaust port of the previously fired cylinder at a uniform time prior to closure of said exhaust port of the previously fired cylinder.

" 53 3 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 692,006 Dted September 19, 1972 Inventor(s) George E. Miller et .211

It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 4, line 34-35; delete "taken generally along line A 6--6", insert-"of the engine incorporated in the outboard motor shown in- I Column 8, line 9; delete "behing"; insert--behind--; Column 9, line 57; delete "intervals", insert interval*-; Column ll, line 44; delete "subsequently fired one of said cylinders", insert---cylinder being charged at the time of the opening of the exhaust gas port of the immediately previously fired cylinder---;

Column 11, lines 64 and 66; delete "structure", insert-- system---. I

Signed and sealed this 19th day of March 'l97L (SEAL) Attest:

EDWARD M.FLE1CHER,JR. "c. MARSHALL DANN 'Attesting Officer Commissioner of Patents 

1. An outboard motor comprising a two-stroke internal combustion engine having a first cylinder bank including a first cylinder and a second cylinder arranged parallel to and in alignment with said first cylinder and having an axis in a first plane containing the axis of said first cylinder, a second cylinder bank including a third cylinder and a fourth cylinder arranged parallel to and in alignment with said third cylinder and having an axis in a second plane containing the axis of said third cylinder, said second plane being at an angle with respect to said first plane, said cylinders each having an exhaust port, means for firing said first, second, third, and fourth cylinders in a predetermined sequential order, a lower unit including a drive shaft housing supporting said engine at the top of said housing, a part which extends, under normal operating conditions, into the water, a propeller supported by said part, and an exhaust gas pipe extending at least partially within said housing and having an upwardly open end adjacent to the top of said housing, and an exhaust gas passageway system located above said one end of said exhaust gas pipe and communicating with said exhaust gas ports and having a downwardly open outlet communicating with said upwardly open end of said exhaust gas pipe, said exhaust gas passageway system providing substantially equal acoustical flow distances between each of said exhaust gas ports and said exhaust gas port of the cylinder being charged at the time of the opening of the exhaust gas port of the immediately previously fired cylinder, said acoustical flow distances having a length such that the compressive wave emanating from opening of the exhaust gas port of the immediately previously fired cylinder arrives at the exhaust gas port of the then being charged cylinder at a time prior to closure of said exhaust gas port of the cylinder then being charged.
 2. An outboard motor in accordance with claim 1 wherein the angle between sAid first plane and said second plane is approximately 90* .
 3. An outboard motor in accordance with claim 1 wherein said exhaust gas ports are open in the area between included angle between said first and second planes.
 4. An outboard motor in accordance with claim 1 wherein said exhaust gas pipe structure includes an area of increased cross section as compared to the cross section of said pipe structure adjacent to said exhaust gas passage system.
 5. An outboard motor comprising an engine having a block including a first cylinder bank having a first cylinder and a second cylinder arranged parallel to and in alignment with said first cylinder and having an axis in a first plane containing the axis of said first cylinder, a second cylinder bank including a third cylinder and a fourth cylinder arranged parallel to and in alignment with said third cylinder and having an axis in a second plane containing the axis of said third cylinder, said second plane being at an angle with respect to said first plane, said engine block also including a face extending generally perpendicularly to a line bisecting the angle between said first and second planes, and cylinders each having an exhaust port, means for firing said first, second, third, and fourth cylinders in a predetermined sequential order, a housing structure supporting said engine and including an outer housing and an exhaust gas pipe extending at least partially within said housing, and an exhaust gas passageway system communicating between each of said exhaust ports and said exhaust gas pipe, said exhaust gas passageway system providing substantially equal acoustical flow distances between each of said exhaust ports and said exhaust gas port of the subsequently fired one of said cylinders, said exhaust gas passageway system including exhaust gas passages in said engine block communicating with said exhaust ports and with said face, said passageway system further including a passage structure connected to said face of said block, having a single exhaust gas outlet communicating with said exhaust gas pipe and located in a surface in a plane at a substantial angle to said face of said block, and internal passageways communicating between said outlet and each of said gas passages such that the acoustical flow path from said outlet to each of said exhaust ports is approximately equal.
 6. An outboard motor in accordance with claim 5 wherein said passage structure is provided with a jacket adapted to contain a flow of cooling water.
 7. An outboard motor in accordance with claim 5 wherein said engine includes a member between and connected to said engine block and said housing structure and said member includes a part connected to said surface of said passage structure and an exhaust gas duct communicating through said part with said outlet of said passage structure and communicating with said exhaust gas pipe of said housing.
 8. An outboard motor in accordance with claim 7 wherein said face of said engine block is at the rear of the outboard motor and said exhaust duct in said member extends downwardly and forwardly.
 9. An outboard motor comprising a two-stroke internal combustion engine having an engine block with more than two cylinders, said cylinders each having an exhaust port, a lower unit including a drive shaft housing supporting said engine block at the top of said housing, a part connected to said drive shaft housing and extending, under normal operating conditions, into the water, a propeller supported by said part, and an exhaust gas pipe extending at least partially within said housing and having one end located adjacent to the top of said housing, and an exhaust gas passageway system located above said one end of said exhaust gas pipe and including an outlet passageway communicating with said one end of said exhaust gas pipe and respective passageways communicating with each of said exhaust ports and with said outlet passageway so as to provide substantially equal acoustical flow distances between each of said exhaust gas ports and said exhaust gas port of the cylinder being charged at the time of the opening of the exhaust gas port of the immediately previously fired cylinder, said acoustical flow distances having a length such that the compressive wave emanating from opening of the exhaust gas port of the immediately previously fired cylinder arrives at the exhaust gas port of the cylinder then being charged at a time prior to closure of said exhaust gas port of the cylinder then being charged.
 10. An outboard motor in accordance with claim 9 wherein said engine block includes three cylinders communicating with said exhaust gas passageway system.
 11. An outboard motor in accordance with claim 9 including four cylinders communicating with aid exhaust gas passageway system.
 12. An outboard motor in accordance with claim 9 wherein said one end of said exhaust gas pipe is upwardly open and said outlet passageway is downwardly open.
 13. An outboard motor in accordance with claim 9 wherein said lower unit includes an adaptor member located between said engine block and said drive shaft housing and including an exhaust gas duct communicating between said outlet passageway and said exhaust gas pipe.
 14. An outboard motor in accordance with claim 9 including a water jacket in cooling relation to said exhaust gas passageway system.
 15. An outboard motor in accordance with claim 9 wherein said lower unit includes an underwater exhaust gas discharge outlet communicating with said exhaust gas pipe.
 16. An outboard motor in accordance with claim 9 wherein said drive shaft housing includes an enlarged conduit portion and wherein said exhaust gas pipe discharges into said enlarged conduit portion and wherein the acoustical flow distances from each of said exhaust port to said enlarged conduit portion is substantially equal.
 17. An outboard motor comprising a two-stroke internal combustion engine having an engine block with more than two cylinders, said cylinders each having an exhaust port, and a lower unit including a drive shaft housing supporting said engine block at the top of said housing, a part connected to said drive shaft housing and extending, under normal operating conditions, into the water, a propeller supported by said part, an exhaust gas pipe extending at least partially within said housing and having an upper end located adjacent to the top of said housing and a lower discharge outlet, and an exhaust gas passageway system located above said one end of said exhaust gas pipe and including an outlet passageway communicating with said one end of said exhaust gas pipe and respective passageways communicating with each of said exhaust ports and with said outlet passageway so as to provide substantially equal acoustical flow distances between each of said exhaust gas ports and said exhaust gas port of the cylinder being charged at the time of the opening of the exhaust gas port of the immediately previously fired cylinder, and so as to provide substantially equal acoustical flow distances between each of said exhaust gas ports and said exhaust gas pipe discharge outlet, said acoustical flow distances between said exhaust gas ports having a length such that the compressive wave emanating from opening of the exhaust gas port of the immediately previously fired cylinder arrives at the exhaust gas port of the cylinder then being charged at a time prior to closure of said exhaust gas port of the cylinder then being charged.
 18. A method of operating a multi-cylinder two-stroke internal combustion engine having more than two cylinders comprising sequentially firing all of the cylinders in a predetermined series, and sequentially causing, with respect to all of the cylinders and for a given engine speed condition, arrival of the compressive wave emanating from the opening of the exhaust port of the previously fired cylinder at the exhaust port of the cylinder then being charged at a uniform time prior to closure of the exhaust port of the cylinder then being charged, aNd also sequentially causing, with respect to all of the cylinders and for a given engine speed condition, generation by the compressive wave emanating from the exhaust port of the previously fired cylinder of a rarefaction wave which arrives at the exhaust port of the previously fired cylinder at a uniform time prior to closure of said exhaust port of the previously fired cylinder. 